1. Field of the Invention
The present invention relates to a cylinder injection type fuel injection valve which is attached to a cylinder head in order to inject fuel directly into a combustion chamber of a combustion engine.
2. Discussion of Background
FIG. 8 is a side view in cross section of a conventional fuel injection valve shown, for example, in Japanese Unexamined Patent Publication JP-A-2- 215963 (a year of 1990). In the Figure, a reference numeral 21 designates a yoke which constitutes an injection valve body in which a coil unit 24 having a core 22, an electromagnetic coil 23 and so on is fixedly installed. A reference numeral 25 designates a plunger. A ring 26 is connected to an end of the plunger and a rod 27 is connected to the other end thereof integrally by a technique such as a connection method using plastic flow, welding or press-fitting. Further a spherical valve 28 is welded to the tip of the rod 27 to be integrally connected. The plunger 25 is inserted in a fuel passage 29 formed in the center of the yoke 21 along the axis direction of the yoke and arranged in the same direction as that of the core 22. A part of the ring 26 is inserted in an inner periphery of one end of the core 22 such that the core 22 is slidable. A return spring 31 is interposed between the plunger 25 and a spring force adjuster 30 screwed in the core 22.
A nozzle 32 is attached to the bottom end of the yoke 21. The nozzle 32 in a cylindrical shape is formed such that a valve seat 33 is formed in an inner portion; a fuel injection nozzle 34 is provided in the downstream side of the valve seat 33; and an element generating swirling force in fuel 35 is fixedly provided on the upstream side of the valve seat 33.
The element generating swirling force in fuel 35 has an annular body portion having a top-like shape. The spherical valve 28 is inserted in the inner diameter portion (inner periphery) of the annular portion so that the spherical valve is guided to be able to move reciprocally in the axis direction. A reference numeral 36 designates a stopper for controlling a moving distance of the spherical valve 28 which is arranged on the top portion of the nozzle 32. A reference numeral 37 designates a fuel supplying port formed in the yoke 21 and a reference numeral 38 designates a connector.
Next, explanation will be given of the operation. The electromagnetic coil 23 is controlled by applying signals of ON and OFF through the connector 38 according to a predetermined duty whereby the electromagnetic coil 23 is excited or deenergized. When the electromagnetic coil 23 is excited, the coil 23, the core 22, the yoke 21 and the plunger 25 form a magnetic circuit, and the plunger 25 and the spherical valve 28 are magnetically attracted on the side of the core 22 simultaneously. Accordingly, a flow passage in an annular shape (minute space) is kept between the spherical valve 28 and the valve seat 33 in a valve-open state.
However, in the conventional fuel injection valve constructed as described in the above, there were drawbacks such that a performance of combustion is largely influenced by ununiformity of fuel atomization caused when fuel is directly injected into the cylinder.